The benefit of priority is claimed based on UK Patent Application No. 0007024.3 filed on Mar. 23, 2000, the complete disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a device (e.g., an extraction hood) for localised containment of extraneous powdered material (e.g., powdered pharmaceutical materials) in a material transfer apparatus.
2. Description of the Related Art
In the field of material transfer technology, it is known to transfer material between a material supply means (e.g., a powder bin) and a material receiving means (e.g., a reaction vessel) using a valve-operated device. A number of valve-operated devices are known.
A basic butterfly valve comprises a simple flap (xe2x80x9cthe butterflyxe2x80x9d) which is rotatable about an axis to increase or decrease the cross-sectional area of an aperture whereby to control the material flow rate between material supply means and material receiving means. The basic butterfly valve is appropriate for a fixed processing arrangement but is unsatisfactory for transfer between discrete material supply means and material receiving means. This has led to the development of the split butterfly valve in which the valve is split through the butterfly in a direction perpendicular to its longitudinal axis. Thus, the split butterfly valve comprises two discrete parts, a first part secured to the material supply means and a second part secured to the material receiving means, each of which permits containment of material in a material supply means or a material receiving means to which the respective part is secured. In use, the split butterfly valve permits the discrete material supply means and material receiving means to be mechanically docked (see FIG. 1) and thereafter operates as a normal fixed valve by controlling material flow rate across the interface. Thus, with reference to FIG. 1(a), the split butterfly valve is shown with the two parts separated and with the material supply means isolated from the material receiving means. In FIG. 1(b), the respective parts of the split butterfly valve are mechanically docked and the butterfly remains closed to contain the material in the respective means. In FIG. 1(c), the butterfly valve is opened to allow material to flow across the valve interface. After transfer is complete, the parts are closed to re-isolate the material supply means from the material receiving means and are mechanically undocked.
During the transfer of potentially toxic materials, there is in general a need to provide a safe and contained local environment at and in the vicinity of the interface of the material supply means (e.g., a powder bin) and the material receiving means (e.g., a chemical reaction vessel). Current operating parameters and acceptable operator exposure levels have increased the need to address certain performance inadequacies of devices such as split butterfly valves during material transfer.
A particular disadvantage of the split butterfly valve is observed when material transfer is complete and the two parts of the valve are closed and undocked. During the transfer process, the edge faces of the open valve are exposed to extraneous material. Furthermore, extraneous material may become entrained on the split joint faces and is exposed when the valve is closed and the two parts are undocked. It will be appreciated that this type of exposure to extraneous material represents a hazard to operators, in particular where the extraneous material is of a toxic nature. It will also be appreciated that cleaning of the apparatus in the open air (i.e., outside a contained environment) is hazardous, e.g., airborne exposure and exposure through handling of cleaning wipes, etc.
Fine powders are capable of being suspended in the local working environment where they may be inhaled by operators with potentially disastrous consequences. In handling dangerous and potentially toxic powdered products, it is imperative that a safe breathing zone is provided for the operator which falls within current acceptable levels of exposure (e.g., within a magnitude of micrograms per cubic meter).
The invention seeks to address the present needs by providing a containment device which reduces the tendency for extraneous material to escape into the working environment of a material transfer apparatus. In particular, the present invention seeks to overcome the impracticality of completely sealing the environment in and around a material transfer apparatus by providing a device for localised containment which greatly improves the safety aspects of the material transfer apparatus and lowers the risk of material contamination.
According to one aspect the present invention, a device is provided for localised containment of extraneous material at and in the vicinity of the interface between a material receiving means and a material dispensing means. The device comprises a container having a containment chamber. The containment chamber has a first open end adapted to receive at least a part of the material dispensing means, a second open end adapted to receive at least a part of the material receiving means, and an air inlet. The device further comprises means for ventilating the interior of the containment chamber whereby extraneous material at and in the vicinity of the interface between the material receiving means and the material dispensing means is transported to a remote location.
Added to the advantages of increased operator safety achievable by minimizing the risk of exposure to extraneous material, the device of the invention also minimizes the risk of material contamination. In the pharmaceutical industry, this is important in enabling the industry""s strict cleanliness and hygiene codes to be met. The device advantageously removes the majority of airborne particulates which might otherwise may be entrained into the material receiving means.
The device of the invention may be adapted to control the flow characteristics and air quality at and in the vicinity of the interface between the material receiving means and the material dispensing means using forced ventilation. Traditionally, forced ventilation falls into three main categories:
1. Up flow of the surrounding air at a velocity which captures the contaminants and carries them along with the air flow and subsequently into a filtration system before being exhausted to atmosphere. Exhaust is accomplished at high level relative to the contaminant source.
2. Down flow of the surrounding air which draws contaminants to a level below that of the typical operators breathing zone. Exhaust is usually accomplished at low level relative to the contaminant source.
3. Cross flow of the surrounding air at an appropriate capture velocity which evacuates contaminants in a horizontal plane. Exhaust and filtration systems may be set at any level when using this technique.
Whilst each forced ventilation system may be used in the device of the invention and has particular advantages and disadvantages, the device is preferably adapted to provide cross flow ventilation. Although it is generally the most difficult system to adopt, cross flow avoids contamination of horizontal upper or lower surfaces which might otherwise occur with vertical air flow (ie up flow or down flow). In other words, it lowers the risk of fallout and settling of powdered particulates and helps to maintain the recommended safe environmental conditions of the operator""s breathing zone and of the operator working area in general.
In adopting the cross flow method (or any other ventilation method), it will be within the capabilities of the man skilled in the art to optimise particulate capture velocities, control the characteristics of the air flow and ensure clean working zones. For example, the free volumetric space through which the forced airflow is channelled may be balanced with the size of the air inlet aperture and the exhaust ducting. Air flow may be induced by any available means (e.g., a fan fitted in-line with an exhaust outlet).
In a preferred embodiment, the interface between a material receiving means and a material dispensing means may be provided with means for controlling the material flow rate. The means for controlling the material flow rate may be positioned at or near to the second end of the containment chamber. The means for controlling the material flow rate may be positioned on or near to the central axis of the containment chamber. Preferably the means for controlling the material flow rate is positioned in a plane substantially normal to the axis of the containment chamber (e.g., the horizontal plane), particularly preferably the normal plane lies in the effective flow path of the cross-flow air.
In a preferred embodiment, the means for controlling the material flow rate is a valve (e.g., a butterfly valve). Preferably the valve is a two-part valve capable of controlling material flow rate between the material dispensing means and the material receiving means. Particularly preferably the two-part valve comprises a first part secured to the material dispensing means and a second part secured to the material receiving means. More preferably the two-part valve is a split butterfly valve.
Preferably the device of the invention is adapted to cause a net inflow of air from the external environment. This lowers the risk of extraneous material reaching the operator working area and breathing zone.
Preferably the device of the invention is adapted to provide a negative pressure differential between the containment chamber and the means for ventilating the chamber. Preferably the device of the invention is adapted to provide a negative pressure differential between the containment chamber and external environment.
Preferably the device of the invention is adapted to minimise turbulence (in order to substantially eliminate particulate suspension and recirculation). Preferably the device of the invention is adapted to provide substantially laminar air flow through the containment chamber thereby essentially eliminating turbulence.
Preferably the means for ventilating the interior of the containment chamber is an exhaust system comprising an elongate exhaust plenum attached to an exhaust outlet. The exhaust outlet may be attached to a filtration means of an acceptable industry standard (e.g., a filtration system providing HEPA quality filtration). Although the exhaust system may comprise one or more exhaust vents at the interface of the elongate exhaust plenum and the containment chamber, the exhaust system preferably has an unrestricted exhaust opening at the interface of the elongate exhaust plenum and the containment chamber. Alternatively the device preferably comprises a perforated exhaust screen at the interface of the exhaust plenum and the containment chamber. Preferably the perforated exhaust screen is arranged to minimise the air flow across the screen. For example, the perforated exhaust screen is arranged such that its face is substantially normal to the air flow.
The elongate exhaust plenum may be secured to the external wall of the containment chamber and extend in an axial or non-axial (e.g., radial) direction (relative to the axis of the containment chamber). Preferably the walls of the elongate exhaust plenum are convergent away from the interface of the elongate exhaust plenum and the containment chamber. The convergence may be stepwise or continuous. In one embodiment, the exhaust plenum has a substantially rectangular pyramidal configuration.
In a preferred embodiment, the containment chamber of the device of the invention comprises a substantially cylindrical body.
Preferably, the substantially cylindrical body terminates at its second end in a truncated cone, wherein the truncated cone is adapted to be seated on or adjacent to the material receiving means.
Preferably, the substantially cylindrical body terminates at its second end in an apertured base plate, wherein the aperture of the apertured base plate is adapted to be seated on or adjacent to the material receiving means. The means for controlling the material flow rate (e.g., a valve) may pass through the aperture and be secured (e.g., bolted) to the base plate.
Preferably, the wall of the containment chamber has a cut-away portion which acts as the air inlet. The cut-away portion may be at or near to the second end of the containment chamber. For example, the cut-away portion may be substantially rectangular. Preferably the cut-away portion is diametrically disposed to the interface of the exhaust plenum and the containment chamber.
In an embodiment of the device of the invention, the whole or a part of the interior wall of the containment chamber is lined by an inner perforated screen. Preferably the inner perforated screen is spaced apart from the interior wall, particularly preferably parallel spaced apart from the interior wall. Preferably the inner perforated screen is arranged to minimise the air flow across the screen. Preferably the inner perforated screen is arranged to optimise the air flow through the screen.
The surface of the inner perforated screen may comprise uniformly or non-uniformly sized perforations. For example, the perforations at or near to the interface of the elongate exhaust plenum and the containment chamber may be of a greater diameter than the perforations elsewhere. Preferably the perforated screen is cut-away at or near to the interface of the exhaust plenum and the containment chamber. Preferably the inner perforated screen exhibits decreased air resistance towards the interface of the exhaust plenum and the containment chamber.
In a preferred embodiment of the device, the external wall of the containment chamber is provided with a port for passing cleaning materials (e.g., wipes) in and out of the containment chamber. Preferably the port is utilised in a bagging technique i.e., soiled cleaning materials are placed in a protective bag fixed to the port and sealed prior to removal.
In an embodiment of the device of the invention, the second end of the containment chamber may be adapted to be seated on the neck of the material receiving means. The device of the invention may be mounted on a lifting arrangement which may be additionally adapted to support the material supply means.
In general, the internal features of the device of the invention are smoothed to assist air flow and reduce powder traps.
The material supply means may be a powder bin of conventional type or any other such arrangement. The material receiving means may be a chemical reaction vessel, mixing machine, sealed packing device or part of a sequential multi-process flow line connection.
It is envisaged that the device of the invention will be used primarily by fine chemical and pharmaceutical product manufacturers. For example, the device could be used in any number of processes including inter alia the seeding of chemical reaction vessels during drug manufacture, the formulation of general chemical compounds and addition of catalysts to chemical processes. The device may be used at both manufacturing and research and development stages since the charging of chemical reactors and drug formulation will become a less hazardous and more reliable step. However, the device will also be of benefit to other manufacturers within the chemical, food and drugs manufacturing industries where potentially toxic materials are transferred (often in very small quantities) between various vessels.
According to a further aspect the present invention, there is provided a material transfer apparatus for transferring material from a material receiving means to a material dispensing means. The apparatus comprises means for controlling the flow rate of material between the material receiving means and the material dispensing means. The apparatus further comprises a device for localized containment of extraneous material at and in the vicinity of the interface between the material receiving means and the material dispensing means. The containment device comprises a containment chamber having a first open end adapted to receive at least a part of the material dispensing means, a second open end adapted to receive at least a part of the material receiving means, and an air inlet. The containment device further comprises means for ventilating the interior of the containment chamber whereby extraneous material at and in the vicinity of the interface between the material receiving means and the material dispensing means is transported to a remote location.
Additional objects and advantages of the invention will be set forth in the description of the preferred embodiments and methods that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations pointed out in the appended claims.